boost/mpi/skeleton_and_content.hpp

// (C) Copyright 2005 Matthias Troyer
// (C) Copyright 2006 Douglas Gregor <doug.gregor -at gmail.com>
// Use, modification and distribution is subject to the Boost Software
// License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Authors: Matthias Troyer
// Douglas Gregor
/** @file skeleton_and_content.hpp
*
* This header provides facilities that allow the structure of data
* types (called the "skeleton") to be transmitted and received
* separately from the content stored in those data types. These
* facilities are useful when the data in a stable data structure
* (e.g., a mesh or a graph) will need to be transmitted
* repeatedly. In this case, transmitting the skeleton only once
* saves both communication effort (it need not be sent again) and
* local computation (serialization need only be performed once for
* the content).
*/
#ifndef BOOST_MPI_SKELETON_AND_CONTENT_HPP
#define BOOST_MPI_SKELETON_AND_CONTENT_HPP
#include <boost/mpi/config.hpp>
#include <boost/archive/detail/auto_link_archive.hpp>
#include <boost/mpi/packed_iarchive.hpp>
#include <boost/mpi/packed_oarchive.hpp>
#include <boost/mpi/detail/forward_skeleton_iarchive.hpp>
#include <boost/mpi/detail/forward_skeleton_oarchive.hpp>
#include <boost/mpi/detail/ignore_iprimitive.hpp>
#include <boost/mpi/detail/ignore_oprimitive.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/archive/detail/register_archive.hpp>
namespace boost { namespace mpi {
/**
* @brief A proxy that requests that the skeleton of an object be
* transmitted.
*
* The @c skeleton_proxy is a lightweight proxy object used to
* indicate that the skeleton of an object, not the object itself,
* should be transmitted. It can be used with the @c send and @c recv
* operations of communicators or the @c broadcast collective. When a
* @c skeleton_proxy is sent, Boost.MPI generates a description
* containing the structure of the stored object. When that skeleton
* is received, the receiving object is reshaped to match the
* structure. Once the skeleton of an object as been transmitted, its
* @c content can be transmitted separately (often several times)
* without changing the structure of the object.
*/
template <class T>
struct BOOST_MPI_DECL skeleton_proxy
{
/**
* Constructs a @c skeleton_proxy that references object @p x.
*
* @param x the object whose structure will be transmitted or
* altered.
*/
skeleton_proxy(T& x)
: object(x)
{}
T& object;
};
/**
* @brief Create a skeleton proxy object.
*
* This routine creates an instance of the skeleton_proxy class. It
* will typically be used when calling @c send, @c recv, or @c
* broadcast, to indicate that only the skeleton (structure) of an
* object should be transmitted and not its contents.
*
* @param x the object whose structure will be transmitted.
*
* @returns a skeleton_proxy object referencing @p x
*/
template <class T>
inline const skeleton_proxy<T> skeleton(T& x)
{
return skeleton_proxy<T>(x);
}
namespace detail {
/// @brief a class holding an MPI datatype
/// INTERNAL ONLY
/// the type is freed upon destruction
class BOOST_MPI_DECL mpi_datatype_holder : public boost::noncopyable
{
public:
mpi_datatype_holder()
: is_committed(false)
{}
mpi_datatype_holder(MPI_Datatype t, bool committed = true)
: d(t)
, is_committed(committed)
{}
void commit()
{
BOOST_MPI_CHECK_RESULT(MPI_Type_commit,(&d));
is_committed=true;
}
MPI_Datatype get_mpi_datatype() const
{
return d;
}
~mpi_datatype_holder()
{
int finalized=0;
BOOST_MPI_CHECK_RESULT(MPI_Finalized,(&finalized));
if (!finalized && is_committed)
BOOST_MPI_CHECK_RESULT(MPI_Type_free,(&d));
}
private:
MPI_Datatype d;
bool is_committed;
};
} // end namespace detail
/** @brief A proxy object that transfers the content of an object
* without its structure.
*
* The @c content class indicates that Boost.MPI should transmit or
* receive the content of an object, but without any information
* about the structure of the object. It is only meaningful to
* transmit the content of an object after the receiver has already
* received the skeleton for the same object.
*
* Most users will not use @c content objects directly. Rather, they
* will invoke @c send, @c recv, or @c broadcast operations using @c
* get_content().
*/
class BOOST_MPI_DECL content
{
public:
/**
* Constructs an empty @c content object. This object will not be
* useful for any Boost.MPI operations until it is reassigned.
*/
content() {}
/**
* This routine initializes the @c content object with an MPI data
* type that refers to the content of an object without its structure.
*
* @param d the MPI data type referring to the content of the object.
*
* @param committed @c true indicates that @c MPI_Type_commit has
* already been excuted for the data type @p d.
*/
content(MPI_Datatype d, bool committed=true)
: holder(new detail::mpi_datatype_holder(d,committed))
{}
/**
* Replace the MPI data type referencing the content of an object.
*
* @param d the new MPI data type referring to the content of the
* object.
*
* @returns *this
*/
const content& operator=(MPI_Datatype d)
{
holder.reset(new detail::mpi_datatype_holder(d));
return *this;
}
/**
* Retrieve the MPI data type that refers to the content of the
* object.
*
* @returns the MPI data type, which should only be transmitted or
* received using @c MPI_BOTTOM as the address.
*/
MPI_Datatype get_mpi_datatype() const
{
return holder->get_mpi_datatype();
}
/**
* Commit the MPI data type referring to the content of the
* object.
*/
void commit()
{
holder->commit();
}
private:
boost::shared_ptr<detail::mpi_datatype_holder> holder;
};
/** @brief Returns the content of an object, suitable for transmission
* via Boost.MPI.
*
* The function creates an absolute MPI datatype for the object,
* where all offsets are counted from the address 0 (a.k.a. @c
* MPI_BOTTOM) instead of the address @c &x of the object. This
* allows the creation of MPI data types for complex data structures
* containing pointers, such as linked lists or trees.
*
* The disadvantage, compared to relative MPI data types is that for
* each object a new MPI data type has to be created.
*
* The contents of an object can only be transmitted when the
* receiver already has an object with the same structure or shape as
* the sender. To accomplish this, first transmit the skeleton of the
* object using, e.g., @c skeleton() or @c skeleton_proxy.
*
* The type @c T has to allow creation of an absolute MPI data type
* (content).
*
* @param x the object for which the content will be transmitted.
*
* @returns the content of the object @p x, which can be used for
* transmission via @c send, @c recv, or @c broadcast.
*/
template <class T> const content get_content(const T& x);
/** @brief An archiver that reconstructs a data structure based on the
* binary skeleton stored in a buffer.
*
* The @c packed_skeleton_iarchive class is an Archiver (as in the
* Boost.Serialization library) that can construct the the shape of a
* data structure based on a binary skeleton stored in a buffer. The
* @c packed_skeleton_iarchive is typically used by the receiver of a
* skeleton, to prepare a data structure that will eventually receive
* content separately.
*
* Users will not generally need to use @c packed_skeleton_iarchive
* directly. Instead, use @c skeleton or @c get_skeleton.
*/
class BOOST_MPI_DECL packed_skeleton_iarchive
: public detail::ignore_iprimitive,
public detail::forward_skeleton_iarchive<packed_skeleton_iarchive,packed_iarchive>
{
public:
/**
* Construct a @c packed_skeleton_iarchive for the given
* communicator.
*
* @param comm The communicator over which this archive will be
* transmitted.
*
* @param flags Control the serialization of the skeleton. Refer to
* the Boost.Serialization documentation before changing the
* default flags.
*/
packed_skeleton_iarchive(MPI_Comm const & comm,
unsigned int flags = boost::archive::no_header)
: detail::forward_skeleton_iarchive<packed_skeleton_iarchive,packed_iarchive>(skeleton_archive_)
, skeleton_archive_(comm,flags)
{}
/**
* Construct a @c packed_skeleton_iarchive that unpacks a skeleton
* from the given @p archive.
*
* @param archive the archive from which the skeleton will be
* unpacked.
*
*/
explicit packed_skeleton_iarchive(packed_iarchive & archive)
: detail::forward_skeleton_iarchive<packed_skeleton_iarchive,packed_iarchive>(archive)
, skeleton_archive_(MPI_COMM_WORLD, boost::archive::no_header)
{}
/**
* Retrieve the archive corresponding to this skeleton.
*/
const packed_iarchive& get_skeleton() const
{
return this->implementation_archive;
}
/**
* Retrieve the archive corresponding to this skeleton.
*/
packed_iarchive& get_skeleton()
{
return this->implementation_archive;
}
private:
/// Store the actual archive that holds the structure, unless the
/// user overrides this with their own archive.
packed_iarchive skeleton_archive_;
};
/** @brief An archiver that records the binary skeleton of a data
* structure into a buffer.
*
* The @c packed_skeleton_oarchive class is an Archiver (as in the
* Boost.Serialization library) that can record the shape of a data
* structure (called the "skeleton") into a binary representation
* stored in a buffer. The @c packed_skeleton_oarchive is typically
* used by the send of a skeleton, to pack the skeleton of a data
* structure for transmission separately from the content.
*
* Users will not generally need to use @c packed_skeleton_oarchive
* directly. Instead, use @c skeleton or @c get_skeleton.
*/
class BOOST_MPI_DECL packed_skeleton_oarchive
: public detail::ignore_oprimitive,
public detail::forward_skeleton_oarchive<packed_skeleton_oarchive,packed_oarchive>
{
public:
/**
* Construct a @c packed_skeleton_oarchive for the given
* communicator.
*
* @param comm The communicator over which this archive will be
* transmitted.
*
* @param flags Control the serialization of the skeleton. Refer to
* the Boost.Serialization documentation before changing the
* default flags.
*/
packed_skeleton_oarchive(MPI_Comm const & comm,
unsigned int flags = boost::archive::no_header)
: detail::forward_skeleton_oarchive<packed_skeleton_oarchive,packed_oarchive>(skeleton_archive_)
, skeleton_archive_(comm,flags)
{}
/**
* Construct a @c packed_skeleton_oarchive that packs a skeleton
* into the given @p archive.
*
* @param archive the archive to which the skeleton will be packed.
*
*/
explicit packed_skeleton_oarchive(packed_oarchive & archive)
: detail::forward_skeleton_oarchive<packed_skeleton_oarchive,packed_oarchive>(archive)
, skeleton_archive_(MPI_COMM_WORLD, boost::archive::no_header)
{}
/**
* Retrieve the archive corresponding to this skeleton.
*/
const packed_oarchive& get_skeleton() const
{
return this->implementation_archive;
}
private:
/// Store the actual archive that holds the structure.
packed_oarchive skeleton_archive_;
};
namespace detail {
typedef boost::mpi::detail::forward_skeleton_oarchive<boost::mpi::packed_skeleton_oarchive,boost::mpi::packed_oarchive> type1;
typedef boost::mpi::detail::forward_skeleton_iarchive<boost::mpi::packed_skeleton_iarchive,boost::mpi::packed_iarchive> type2;
}
} } // end namespace boost::mpi
#include <boost/mpi/detail/content_oarchive.hpp>
// For any headers that have provided declarations based on forward
// declarations of the contents of this header, include definitions
// for those declarations. This means that the inclusion of
// skeleton_and_content.hpp enables the use of skeleton/content
// transmission throughout the library.
#ifdef BOOST_MPI_BROADCAST_HPP
# include <boost/mpi/detail/broadcast_sc.hpp>
#endif
#ifdef BOOST_MPI_COMMUNICATOR_HPP
# include <boost/mpi/detail/communicator_sc.hpp>
#endif
// required by export
BOOST_SERIALIZATION_REGISTER_ARCHIVE(boost::mpi::packed_skeleton_oarchive)
BOOST_SERIALIZATION_REGISTER_ARCHIVE(boost::mpi::packed_skeleton_iarchive)
BOOST_SERIALIZATION_REGISTER_ARCHIVE(boost::mpi::detail::type1)
BOOST_SERIALIZATION_REGISTER_ARCHIVE(boost::mpi::detail::type2)
BOOST_SERIALIZATION_USE_ARRAY_OPTIMIZATION(boost::mpi::packed_skeleton_oarchive)
BOOST_SERIALIZATION_USE_ARRAY_OPTIMIZATION(boost::mpi::packed_skeleton_iarchive)
#endif // BOOST_MPI_SKELETON_AND_CONTENT_HPP